Asitha Athukorala

Experimental Depiction of the Hypothesis of Flake-Like Wear Debris Generation in Rolling Contact Fatigue of the Rail–Wheel Contact Interface

ABSTRACT Flake-like particles represent a common type of wear debris generated during the rolling contact fatigue wear test using a twin-disc test rig. It is argued that these flake-like particles are generated during the delamination process due to plastic shear strain accumulation at the wearing surfaces. This hypothesis has been developed in the last decades to explain the particle generation mechanism, yet it has not been proven conclusively. This research provides strong experimental evidence of the creation processes of wear debris propagation, aggregation, transfer, and compaction, therefore confirming the existing hypothesis and enhancing the understanding of wear mechanisms in the rolling contact interface.

Wear Particle Analysis and the Evolution of the Plastically Deformed Layer on Australian Rail Steel

Particle analysis methodology is presented, together with the morphology of the wear debris formed during rolling contact fatigue. Wear particles are characterised by their surface topography and in terms of wear mechanism. Rail-wheel materials are subjected to severe plastic deformation as the contact loading progresses, which contributes to a mechanism of major damage in head-hardened rail steel. Most of the current methodologies involve sectioning of the rail-wheel discs to trace material damage phenomena such as crack propagation and plastic strain accumulation. This paper proposes methodology to analyse the development of the plastically deformed layer by sectioning wear particles using the focussed ion beam (FIB) milling method. Moreover, it highlights the processes of oxidation and rail surface delamination during unlubricated rolling contact fatigue.